Operating in areas where the temperature of the atmosphere is in the sub-zero range produces several undesirable effects upon the human body. This is especially experienced by mountain climbers polar explorers, and others encountering similar environments. The first of these, of course, is loss of heat directly from the body surface and its attendant discomfort. The second is the inspiration of very cold dry air which has the combined effect of loss of body heat and difficulty in breathing. An added and related problem is the effect of inspiration of very dry air and consequent loss of moisture from the body which further aggravates the above conditions.
The manner in which body heat is lost has been studied by the Naval Medical Center at Bethesda, Md. and tabulated in the U.S. Navy Polar Manual as follows:
1. Direct loss from body surface -- 63% to 70% PA1 2. Evaporation of perspiration -- 14% to 18% PA1 3. Saturation of inspired air with water vapor -- 8% to 9% PA1 4. Warming of inspired air -- 2% to 9% PA1 5. Warming of ingested foods and fluids to body temperature -- 1% or less.
By drawing inspired air from within the clothing, some heat loss directly from the body surface would be recaptured. When warm air is inspired instead of cold air, the heat loss occasioned by warming the latter is reduced. Air drawn from within the clothes also contains perspiration vapor which by purification through a simple filter can be made to retain a substantial part of its moisture, thus increasing its humidity and improving its breathing qualities. An added advantage is that in removal of the moisture in the clothes, the heat conduction is decreased and the insulating efficiency of the clothing improved, thus further decreasing the heat lost directly from the body surface.
Thus it is seen that not only warming of the inspired air would effect considerable saving in body heat but also elimination of the necessity for saturating the inspired dry air would have a like effect. What is produced in effect is a recycling of body moisture and the elimination of dehydration of the body.
The physiological effects of body chilling and dehydration are well known. They generally manifest themselves by a greater strain on the heart, increased blood pressure and pulse rates, increased urinary output often manifesting itself in headaches, indigestion, fatigue, and frost bite. These, in general, are the bad effects which recycling of the body heat and moisture as described herein, eliminates.
This problem has been recognized for some time as evident from the above reference. Several attempts have been made to solve it and the prior art, as known to the applicant at this time, is summed up briefly below.
U.S. Pat. No. 3,229,681 to Gluckstein utilizes a breathing or inhaling mask in combination with a chemical catalyst compartment which warms the air as it is being inspired.
U.S. Pat. No. 3,249,108 to Terman utilizes an electrical battery heated apparatus to warm the air on its way to the breather's mask.
U.S. Pat. No. 3,491,754 to Weese and U.S. Pat. No. 3,707,966 to Nebel both attempt to use body temperature in one way or another to heat incoming air. Weese uses a two layer pad with a simple tube leading to the mouth of the user. It necessitates heavy pressure against the chest, is rather bulky and provides no direct connection to the environment. Nebel employes a similar pad which has disadvantages similar to those of Weese. Both these devices are confined to only a small and localized area of the body and thus cannot possibly effect an efficient recycling operation as does the applicant. They cannot maintain close contact with the body which moves and angles considerably during climbing operations. Neither of these devices provide for moisture control.